C. L. Rutheroff revealed designs for transmission line transformers in, "Some Broadband Transformers", Proceedings of the IRE, Volume 47, August 1959, pp 1337-1342. These devices had very wide bandwidth characteristics, some ratios as high as 20,000:1. Frequency ranged from a few tens of kilohertz to over one thousand megahertz. While the devices described in Rutheroff's paper were made of twisted pair transmission lines wound on ferrite torroids, it was there suggested that any kind of a transmission line might be used. The 4:1 impedance transformer circuit of FIG. 1 is representative of the sort of transformer which Rutheroff converted to transmission line form. Rutheroff, supra at p. 1338. The advantage of the devices described were stated as follows: "In transmission line transformers, the coils are so arranged that the interwinding capacity is a component of the characteristic impedance of the line, and as such forms no resonances which seriously limit the bandwidth." Rutheroff, Supra, at p. 1337.
O. Pitzalis, Jr. and T. P. M. Couse published, "Broadband Transformer Design for RF Transistor Power Amplifiers", in the Electronics Components Conference Proceedings, May 1968. This paper specifically suggested that short coaxial cable lengths could be utilized to build the transformers proposed by Rutheroff at the higher frequencies. Pitzalis et al further analyzed the circuits of FIGS. 1 and 4 (a 0:1 impedance matching transformer) among others.
Operation of these prior art transformer systems is degraded by inductance introduced in the interconnections between any two or more ends of the coaxial cable. The degradation is caused by the relatively high series reactance produced by even small inductance values at higher frequency ranges. In many applications it is a further requirement to provide a rugged mounting of the coaxial cable sections to prevent physical degradation or even destruction of the transformer component parts. Prior art coaxial cable R.F. transformers have suffered limitations in these areas.